Minerals building blocks of rocks

• An element is a substance that cannot be broken down into simpler substances by chemical means • Minerals are made up of one or more elements... Atoms, molecules and ions• Atoms are t

Minerals

Minerals: Building blocks of rocks

To be considered a mineral, a substance must:

• be a naturally occurring solid

• be formed by inorganic processes

• have a crystalline structure (orderly molecular arrangement)

• have a specific chemical composition

• An element is a substance that cannot be

broken down into simpler substances by

chemical means

• Minerals are made up of one or more elements

Most abundant elements of the

Atoms, molecules and ions

• Atoms are the smallest

individual particle that

retains the distinctive

chemical properties of an

element

• Molecules are the smallest

individual particle that

retains the distinctive

chemical properties of a

chemical compound

Molecules consists of 2 or

more atoms

• Ions are atoms or

molecules that have a net

electrical charge They

attract oppositely-charged

ions to form chemical

compounds

Crystalline Nature of Minerals

Luster: Appearance of a mineral in

reflected light

• Metallic (pyrite)

Nonmetallic: glassy/pearly

(potassium feldspar)

Luster: Appearance of a mineral in

Other Physical properties of

minerals

• Streak

• Color of a mineral in its powdered form

• Helpful in distinguishing different forms

of the same mineral

• Hardness

• Resistance of a mineral to abrasion or

scratching

• All minerals are compared to a standard

scale, the Mohs Scale of Hardness.

Streak – the color of

a powdered mineral

Figure 2.10

• Tendency to break along planes of

weak bonding

• Produces flat, shiny surfaces

• Described by resulting geometric

shapes, and

– Number of planes

– Angles between adjacent planes

Three examples of perfect cleavage – fluorite, halite,

and calcite

Copyright © 2006 Pearson Prentice Hall, Inc.

Common cleavage directions

Classification of Minerals

Rock-forming minerals

• Common minerals that make up most of

the rocks of Earth’s crust

• Only a few dozen members

• Composed mainly of the 8 elements that

make up over 98% of the continental crust

8 most common elements

Classification of Minerals

• In most cases, minerals are grouped

according to the major “building

block” in the chemical structure

Rock-forming Minerals – The Silicate

Group

• Most common mineral

group due to large amounts

of silicon and oxygen in

Earth’s crust

• Basic building block is the

silicate ion: Four oxygen

ions surrounding a much

smaller silicon ion

• Polymerization: process by

which silicate ions bond to

form more complex ions,

such as rings, chains,

sheets or 3 dimensional

frameworks

Common Silicate minerals

• Olivine Group

http://www.youtube.com/watch?v=wFRB6T4AJbs

– High temperature Fe-Mg silicate

– Individual silicate linked together by iron and magnesium ions

– Forms small, rounded crystals with no cleavage

Common Silicate minerals

Common Silicate Minerals

• Amphibole Group

http://www.youtube.com/watch?feature=endscreen&v=fBMeVK_O3HQ&NR=1

– Double chain structures involving a variety of ions linking the silicate ion

– Two perfect cleavages at non right angles

amphibole group

Common Silicate Minerals

Common Silicate Minerals

– (potassium feldspar) (e.g Orthoclase or Microcline)

– Plagioclase (sodium and calcium feldspar) are the two most common members

Feldspar Minerals

http://www.youtube.com/watch?v=zGyaM29yxKI&feature=related

Potassium feldspar - Orthoclase

Copyright © 2006 Pearson Prentice Hall, Inc.

Calcium-rich plagioclase feldspar

http://www.youtube.com/watch?v=eWSpnr9QX74

Chert – Cryptocrystalline Quartz

Nonsilicate mineral groups

Fluorite (left, calcium fluoride) and halite (right, sodium chloride) are

members of the Halide mineral

group The minerals in this group have, as part of the chemical

structure, an ion from the halogen elements: Fl1- , Cl1- , I1- , or Br1-

Gypsum (calcium sulfate) is a member of the sulfate group The building block for minerals in this group is the sulfate ion, SO42-

The Carbonate Group

exposed to acid (as

shown in the video).

“Strong bones, strong teeth”

Nonsilicate Rock-forming mineral